The present invention relates to a drive unit for driving a carriage travelable along a transport path having a barrel cam which can be driven to make a rotational movement and which has a drive groove for an engagement of a follower arranged at the carriage, and having a control device for controlling the drive of the carriage.
Such drive units are used in assembly and automation engineering, for example, to move travelable carriages having workpieces arranged thereon positionally accurately to the corresponding machining and/or assembly stations. In this respect, a transfer of the carriages from a separate drive unit—such as from a belt drive—to a drive unit having a barrel cam may be necessary. It is, however, difficult in practice to coordinate the arrival of the carriages at a continuously or intermittently rotating barrel cam with the barrel movement such that the followers of the carriages engage into the drive groove of the barrel cam as a result of the movement. It is therefore possible that the carriages have to be braked a lot or even stopped before the transfer to the barrel cam, which reduces the effectiveness of the total system. It is equally unfavorable with respect to the effectiveness to move the barrel cam into a defined rotational position for the takeover of a carriage since, as a rule, at least one follower of a preceding carriage is in engagement with the drive groove and would then be moved by adopting the rotational position. That is, the reception of a carriage in the drive region of the barrel cam thus influences the movement of the carriage preceding it, which is unwanted as a rule.